E-Bike Parts

Derailleurs

Rear derailleurs, hangers and shifters for common e-bike drivetrains.

Rear derailleurs get bent when a bike tips over onto its drive side, which e-bikes do often thanks to their weight and kickstand leverage. The result is sloppy shifting, a chain that drops, or a derailleur that swings into the spokes. Before buying a new derailleur, check the hanger, the small replaceable piece between frame and derailleur; it is designed to bend first and is cheap. A straight hanger fixes a lot of misdiagnosed derailleurs. The fix costs a few dollars and ten minutes, so always check it before anything else.

If the derailleur itself is damaged, match three things. Speed count must match your shifter and cassette or freewheel. Brand and series matter because cable pull ratios differ: Shimano and SRAM are not interchangeable, and within Shimano some newer mountain series pull differently from older ones. Many hub-drive e-bikes use Shimano Tourney or Altus 7-speed derailleurs, which are inexpensive and widely available. Cage length and maximum cog size must suit your cassette range.

Shifters follow the same rules: speed count and compatible pull ratio with the derailleur. Trigger and twist styles are interchangeable as long as the pull matches, but check bar space around your throttle and brake lever. Derailleur hangers are frame-specific; the bike maker or a hanger finder site is the reliable source. Confirm on your bike that the derailleur's pull ratio and capacity match before ordering. If you are unsure of the series, the model number is printed on the back of the derailleur body and on the shifter, and a photo of both makes matching straightforward.

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Derailleurs

Shimano Altus RD-M310 7/8-Speed Rear Derailleur

The Altus M310 is a step up from Tourney and the common derailleur on 8-speed e-bikes; it also works with 7-speed shifters, which makes it a popular upgrade when a TY300 dies. It mounts to a standard derailleur hanger (no claw version), handles up to a 34T cog, and shifts noticeably crisper than Tourney. It is still inexpensive. If your bike uses a direct-mount claw bracket, you will need an adapter or to stay with Tourney. Replace the shift cable at the same time and check the hanger alignment.

Best for: 8-speed e-bikes needing a replacement derailleur · 7-speed bikes with a standard hanger that want crisper shifting · Riders running a 34T low cog

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Derailleurs

Shimano SL-TX50 7-Speed Thumb Shifter (Right)

The SL-TX50 is the simple thumb shifter that comes on many 7-speed e-bikes, especially ones with a twist throttle on the right that leaves no room for a grip shifter. It is a right-hand, 7-click indexed shifter with an optical gear indicator, and it clamps onto a 22.2 mm bar. When the index gets sloppy or the lever breaks, this is the cheap, direct replacement. Shifters are sold with a cable, which you should install new; most shifting problems on budget e-bikes are cable friction rather than the shifter itself.

Best for: 7-speed e-bikes with a broken or worn thumb shifter · Bikes where a twist shifter conflicts with a twist throttle · Budget replacements

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Derailleurs

Shimano Tourney RD-TY300 6/7-Speed Rear Derailleur

The Tourney TY300 is the derailleur on an enormous number of 7-speed e-bikes, and it is what you buy when the original gets bent by a fall or a stick. It is cheap, easy to set up, and available in a few mounting styles: a direct-mount version with a bracket (claw) for bikes without a hanger and a standard-hanger version. Before ordering, look at how your old derailleur attaches. It shifts fine for a 7-speed hub-motor bike and pairs with the stock thumb or trigger shifters; just expect to replace the cable at the same time.

Best for: 7-speed hub-motor e-bikes with a bent or broken derailleur · Budget like-for-like replacements · Riders who want a part that matches the stock shifter

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How to choose derailleurs

Speed count

Match your shifter and rear cogs exactly.

Brand and pull ratio

Stay within a compatible family. Shimano 7, 8 and 9 speed mountain parts are broadly compatible with each other; newer 10 and higher and all SRAM parts follow their own rules.

Cage length and capacity

Long cage for wide-range cassettes and front derailleur setups; short cage for tight ranges. Check the max cog size against your largest cog.

Mount type

Standard hanger mount is most common; some bikes use direct mount. Hangers are frame-specific.

Shifter style and clearance

Trigger or twist; confirm it fits beside your throttle, brake lever and display.

Compatibility notes

Derailleur and shifter pull ratios must match; Shimano and SRAM do not mix, and some Shimano series do not mix with each other. Confirm on your bike.
Derailleur hangers are frame-model specific; confirm with the bike maker or a hanger database.
Maximum cog size must meet or exceed your cassette's largest cog.

Installation considerations

Check and straighten or replace the hanger first, ideally with an alignment gauge.
Bolt on the new derailleur, thread the cable, and set high and low limit screws before indexing.
Adjust cable tension with the barrel adjuster until shifts are crisp in both directions.
Check that the derailleur cannot reach the spokes in the lowest gear.

Maintenance tips

Keep pivots lightly lubricated and the pulley wheels free of packed grime.
Re-index after cable stretch in the first few rides with a new cable.
Lay the bike down on its non-drive side, or use the kickstand carefully, to avoid bending the hanger.

E-Bike Chain Keeps Falling Off

Frequently asked questions

Is my derailleur bent or the hanger?

Sight from behind: the derailleur cage should hang parallel to the cogs. If it angles inward, the hanger is bent and often fixable; if the derailleur body or cage is twisted or cracked, replace the derailleur.

Can I use a SRAM derailleur with a Shimano shifter?

Generally no; the cable pull ratios differ and shifting will not index. Stay in one brand family unless a specific pairing is documented.

Which derailleur do most hub-motor e-bikes use?

Many use Shimano Tourney or Altus 7-speed units, which are inexpensive and easy to find. Check the model printed on your current derailleur.

Where do I get a hanger for my bike?

From the bike maker, or by matching your frame in an online hanger database. Take a clear photo of both sides of the old hanger to compare shapes.

Do I need a new shifter with a new derailleur?

Only if the speed count or pull ratio changes. Same-family replacements work with your existing shifter.